Magnetic fluid mixture brake



NOV. 11, 1952 FElERTAG 2,617,507

MAGNETIC FLUID MIXTURE BRAKE Filed Dec. 2, 1949 Fig.2,

Fa l.

, Inventor: Karl M- Fe'levtag, y HisAttorney.

larity in'-'the claims annexed to and forming Patented Nov. 11, 1952 uNITEosTArrs PATENT OFFICE MAGNETIC'FLUID MIXTURE BRAKE Karl M. Feiertag, Fort Wayne, Ind., assignor to General Electric New York in Company, a corporation of Application December 2, 1949, Serial No. 130,682

*tional engagement, and in the eddy current de- 'yices large eddy currentsurfaces must be provided with complicated cooling arrangements;

It is therefore desirable to provide a clutch or brake wherein'the braking torque or driving connection neither depends on frictional engage- "iAn objector this invention is to provide an .improved brake.

"Another object of this invention is to provide 'an improved clutch.

"A further object of this invention is to provide an improved brake wherein the braking torque is provided without frictional'engagement or; the -"utilization of-eddy currents. Y Af-still further object of this invention is to provide an improved clutch wherein the driven *ecnne'cuo is established without frictional eng'a'ge'xnent-or'the utilizationof eddy currents.

' Further-objects and advantages of -this invention will become apparent,'and the invention will bebett'e'r understood from the following dESOIl-P'.

'tionreferring to the accompanying'drawing,

" 7 Claims. (01. 192-215) and thefeatures of novelty which'jcharacterize 7 this invention will be pointed out with particupartof this specification. I -In accordance with this invention, thereare provided inner and outer relatively rotatable members, the inner member comprising a permanent magnet polarized axially and a pair of annular pole piece members abutting the ends of the'permanent magnet. The outer extremities of the pole piece members are spaced apart with the adjacentfaces-adjacent the outer circumferential edges" defining an air gap. A non-magnetic "spacer member is positioned in the air gap and has a circumferential groove formed in its outer "surfaces The outer member has an annular exciting winding surrounded by a magnetic casing. A circumferential groove is formedin the inner circumferential surface of the casing, and the in her circumferential surface portions of the casing on either side of the groove respectively form air gaps with the outer circumferential edges of the pole piece'members. A magnetic fluid mixture, for instance one having magnetic iron particles suspended in oil, is arranged in the. air gaps between the casing and the pole piece members and the permanent magnet produces flux which traverses these air gaps and the casing,

when the winding is not not energized. This permanent magnet flux solidifiesthe; magnetic fluid mixture in the air gaps between the casing and the pole piece members preventing relative rotation of the inner and outer members. winding is arranged when energized to produce The fluxin the casing opposing the permanent magnet flux so that no permanent magnet flux traverses the air gaps between the casing. and the pole pieeemembers. The flux produced by the winding therefore crosses the circumferential groovein the casing and the permanent magnet flux crosses the air gap between the pole piece members thus diverting the magnetic fluid mixture into the two grooves releasing the connection between the two members so that relative rotation is permitted.

In the drawing, Fig. 1 is a side elevation view partly in section illustrating the improved brake of this invention with the braking connection established; Fig. 2 is a fragmentary view of the device of Fig. 1 shown with the braking connection released; Fig. 3 is a schematic illustration showing a'series motor provided with the improved brake of this invention; and Fig. 4isa side elevation viewpartly in section illustrating the application of this'invention to a clutch.

- Referring now to Fig. 1, there is shown a rotatable shaft I havinga rotatable member'generally 'identified'as 2 mounted thereon. The rotatable member 2 is formed of a cylindrical permanent magnet 3 having an opening 4 formed therein to receive the shaft I'. The permanent magnet 3 is polarized'axially to form polar areas at its ends as shown in Fig. l. A pair of annular flux conducting pole piece members 5' and 6 are mounted on the shaft I and respectively abut the ends of the permanent magnet 3. Inthei event that the shaft I is formedof magnetic material, it is'desirable'that the opening 4 of the permanent magnet 3 be sufilciently large to permit the permanent magnet to be spaced from the shaft I and the pole pieces 5 and 6 are therefore secured to the shaft I by non-magnetic bushings I. The outer extremities 8 and 9 of the pole'piece members 5 and'6 are spaced apart so that'the adjacent faces l0 and spacer I5. portions 23 and 21 on eithersideofthe circumferential groove 24 respectively form air gaps ll adjacent the outer circumferential edges I2 and I3 define an air gap M. A non-magnetic spacer member I is positioned in the air gap l4 and is provided with a circumferential groove H5 in its outer surface.

The shaft is rotatably supported by suitable bearings I! carried by a stationary bearing housing member |8 formed on stationary frame member 19. A stationary member generally identifled as is secured to the stationary frame l9 and includes an annular exciting coil 2|, adapted to be energized by an external source of power (not shown) by lines 22. The annular exciting winding 2| is surrounded by a magnetic casing member 23 having a circumferential groove 24 formed in its inner circumferential surface. The circumferential groove 24 forms a restricted section 25 in the inner circumferential surface of the magnetic casing 23 and is concentric with the circumferential groove 16 in the non-magnetic The inner circumferential surface 28 and 29 with the other circumferential edges 1 l2 and I3 of the pole piece members 5 and 6.

In order to provide a braking action, a sufiicient quantity of a magnetic fluid mixture 30, for instance magnetic iron particles suspended in oil,

is arranged in the air gaps 28 and. 29 filling the same when operative, as will be hereinafter de- 3.

scribed. When the winding, 2| is not energized,

. the permanent magnet 3 produces fluxtraversing the air gaps 28' and 29 and the magnetic casing 23 as shown by the arrows 3|. A small amount. of permanent magnet flux may cross the air gap ['4 as shown by the arrow 32.

By virtue of thefiux 3| crossing the air gaps 28 and 2-9,. the magnetic fluid 30 will be solidified, applying braking torque on the rotatable member 2. Referring now to Fig.2, .the coil 2|-'is arranged to produce. flux when energized inthe casing member 23 in a direction to oppose the permanent magnet flux 3|. as shown by the arrows 33. The

winding 2! should preferably be designed to produce M. M. F. sufficient to provide a number of flux lines in the casing 23, except in the restricted section 25, equal to or somewhat in excess to the number offlux lines produced by the permanent magnet3, taking into consideration the width of the-"gaps 2-8 and 29, the length of themagnetic path, etc.

Sucha. fluxv in the casing 23 will cause the reduced section 25 to become saturated and, as a result, some of the flux will cross the circumferential groove. 24, as shown by the-arrow 34: Due to the opposition of the exciting'winding' flux'33to the permanent magnet flux 3 no flux will traverse the air gaps 28' and '29'causing the permanent magnet flux. to traverse the gap l4 and the circumferential groove l5, as shown by the arrow 35. Thus, a, substantial portion of the magnetic fluid mixturetll is di- I verted to the circumferential grooves I6 and 24 'by' the fluxes 34 and 35 removing the magnetic fluid from the gaps 28 and 29 releasing the brakingtorque. from the rotatable member 2.

Referring now to Fig. 3, the exciting winding 2| of the brake. of Figs. I and 2 may be arranged series with a series field exciting winding 35 of series motor 31v which is energized by an externalsource of power (not shown) by lines 38.:

' brake will also be energized and no braking torque will be applied to the rotatable member 2. However, as soon as the motor 3'! is deenergized, the

, exciting winding 2| will also be deenergized so is always in the solidified state, either in the tion.

air gaps 28 and 29 under the influence of the permanent magnet flux 3|, or in the circumferential grooves l6 and 24 under the influence of exciting winding flux 34 and permanent magnet flux 35.

Referring now to Fig. 4 in which like parts are indicated by like reference numerals, there is shown a clutch wherein the outer member 20 is mounted on rotatable shaft 39 by means of a flange member 40 keyed to the shaft 39 in any suitable manner. The exciting winding 2| is energized through'slip rings 4| on the shaft 39. It will be readily apparent that when the exciting winding 2| is not energized, the permanent magnet flux-3| wiil'traverse. the-air gapszffl 29 and the magnetic casing 23 solidifying the mag- 'flux 35- crossing the circum erential groove t6 divert the magnetic fluid mixture 3|! into the grooves H5 and releasingthe driving connec- It will now bereadily apparent -that this in.- vention provides an improved brake plutch construction wherein no moving parts neces- --'sary, the periodic replacement; of: a frictional brake or clutch surface is obviated, andno' cooling is necessary as in the case of an eddy current device. It will also be readily apparent that the amount of energization of the winding 2| will determine the amount of braking action so that overspeed or over-running can lee-prevented and in both the clutch and brake embodiments, the

- ac tio r 1 is inherently smooth. It will bev further apparent that th improved evice of thisinvention, when usedas a brake, fails safe sinee the braking connection is established-when the coil is not energized. In addition, the device functions as anoverload clutch. Itcanbe seen that .thisconstructionis desirable for-e rnagnetic coupling, for instance, from a synchronous motor to a load, since the coil. can be energized while the motor is broughtup to speed at which point the'coil excitation can be gradually reduced to establish the driving connection after which the coupling is operated with the permanent magnet alone requiring no energization on the'coil.

While I have illustrated and describedparticular embodiments of this inventiom'modifications' thereof will occur to those skilled in the art. I desire it to be understood, therefore. that this invention is not to be limited to the particular arrangements disclosed, and I intend in the appended claims to cover all modifications. which do not depart from the-spirit. and scope of this invention. 7 v

What I claim as new and; desire to secure by Letters Patent of theUnited States is: 1. In combination; a pair of reiativelyrotatabl members,- one of said members comprisingm ljair gap and having a circumferential groove {formed in its outer surface, said outer member extremities of said pole piece members defining 1 anair gap therebetween, the other of said mem- 5 bers comprising an exciting winding and a magnetic casing member surrounding said windmg,=- said magnetic casing member being positioned adjacent said pole piece member respectively forming air gaps therewith, said last men:

tidned air gaps having a magnetic fluid mixture"arranged therein, said permanent magnet producing flux traversing said last mentioned air gaps and said magnetic casing when said winding is not energized so that said magnetic fluid is solidified whereby relative rotation of said relatively rotatable members is prevented, said Winding being adapted when energized to produce flux in said casing in a direction to op-l pose said permanent magnet flux so that 110x permanent magnet flux traverses said last mentioned air gaps whereby the flux produced by" said'winding diverts a portion of said magnetic fluid mixture from said last mentioned air gaps permitting relative rotation of said relativelyrotatable members.

2,- In combination, inner and outer relativelyiotatable members, said inner member comprising a permanent magnet polarized axially to i farm polar areas atits ends and a pair of an nular flux conducting pole piece members respectively abutting the ends of said permanent, magnet, the outer extremities of said pole piece members being spaced apart with the adjacent; faces thereof adjacent the outer edges of saidpole piece members respectively defining an air: gap, said outer member comprising an annular. exciting winding and a magnetic casing member surrounding said winding, the inner cir: cu mferential surface of said casing respectively? forming air gaps with the outer circumferential edges of said pole piece members, said last mentioned air gaps having a magnetic fluid mixture arranged therein, said permanent magnet pro ducing flux traversing said last mentioned air-" gaps and said magnetic casing when said winding is not energized so thatthesaid magnetic fluid is solidified whereby relative rotation of said rotatable members is prevented, said windifig being adapted when energized to produce flux in said casing in a direction to oppose said permanent magnet flux so that no permanent agnet flux traverses said last mentioned air,

ps whereby the flux produced by said winding diverts a portion of said magnetic fiui mixture from said last mentioned air gaps per-' mitting relative rotation of said relatively rotatable members.

3. In combination, inner and outer rotatable members, said inner member comprising permanent magnet polarized axially to form; ipo'lar areas at its ends, a pair of annular flux conducting pole piece members respectively abutting the ends of said permanent magnet, the. outer extremities of said pole piece members bee ing spaced apart with adjacent faces adjacentithe outer edges of said pole piece members re- ;ls pectively defining an air gap, and an annular non-magnetic spacer member positioned in said comprising an annular exciting winding and .a magnetic casing member surrounding said wind ing with a circumferential groove formed in its inner circumferential surface, the inner cir t6 cumferential surface portions of said casing member on either side of said circumferential groove respectively forming air gaps with the outer circumferential edges of said pole piece members, said last mentioned air gaps havinga magnetic fluid mixture therein, said permanent magnet producing flux traversing said last mentioned air gaps and said casing when said winding is not energized so that said magneti'c fluid isv solidified whereby relative rotation of said relatively rotatable members is prevented, said winding when energized being adapted to produce flux in said casing in a direction toonpose said permanent flux so that no permanent.

flux traverses said last mentioned air gaps whereby the flux produced by said winding diverts a portion of said magnetic fluid mixture from said last named air gaps to said circumferential groove in said magnetic casing member permitting relative rotation of said rotatable members.

4. A brake for rotatable apparatushaving-a rotatable member and a stationary member, one of said members comprising a permanent magnet and a pair of flux conducting pole piecemembers respectively abutting the polar areas of said permanent magnet, the outer extremities of said pole piece members defining an air gap therebetween, the other of said members comprising an exciting winding and a magnetic casing member surrounding said winding, said magnetic casing member being positioned adjacent said pole piece members respectively forming air gaps therewith, said last mentioned air gaps having a magnetic fluid mixture arranged therein, said permanent magnet producing flux traversing said last mentioned air gaps and said casing when said winding is not energized so that said magnetic fluid is solidified applying braking torque on said other member, said winding being adapted when energized to produce flux in said casing in a direction to oppose said permanent flux so that no permanent flux traverses said last mentioned air gaps whereby the flux produced by said winding diverts a portion of' said magnetic fluid mixture from said last mentioned air gaps releasing said braking torque.

5. A brake for rotatable apparatus having an inner rotatable member and an outer stationary member, said rotatable member comprising a permanent magnet polarized axially to form polar areas at its ends and a pair of annular flux conducting pole'piece members respective-- ly abutting the ends of said permanent magnet, the outer extremities of said pole piece members being spaced apart with adjacent faces adjacent the outer edges of said pole piece members respectively defining an air gap, said sta-- tionary member comprising an annular exciting winding and a magnetic casing member surrounding said winding, the inner circumferential surface of said casing respectively forming air gaps with the outer circumferential edges of said pole piece members, said last mentioned air gaps having a magnetic fluid mixture arranged therein, said permanent magnet producing flux traversing said last mentioned air gaps and said casing when said winding is not energized sov that said magnetic fluid is solidified applying braking torque on said rotatable member, said winding being adapted when energized to produce flux in said casing in a direction to oppose said permanet magnet flux so that no permanent flux traverses said last mentioned air gaps whereby" the flux produced-by said winding. diverts-a portion or said magnetic fluid mixture from said last mentioned. airgaps releasing said braking torque.

6.. A brake for rotatable apparatusihaving a rotatable shaft, a rotatable member mounted on said shaft comprising a permanent magnet polarized axially to form polar areas at its. ends,

.a pair of flux. conducting annular pole piece .members respectively abutting the ends oi said permanent magnet, the outer extremities of. said pole piece members. being spaced apart with. adjacent faces adjacent the outer circumferential edges of said pole piece members respectively defining an air gap, and. an. annular nonmagnetic, spacer member positioned in said air gap with acircumferential groove formed. in the outer surface thereof, and a stationary member surrounding said rotatable member comprising an annular exciting winding; and. a;

magnetic casing member surrounding said Wind.- ing and having a circumferential groove formed in. its. inner circumferential; surface, the inner circumferential surface portionsrof said casing on either side of said groove respectively forming air gaps with the outer circumferential edges 'of said pole piece members, said last mentioned air gaps having a magnetic fluid. mixture ar ranged therein, said permanent magnet producing flux traversing said last mentioned air gaps and said casing whenv said. winding 1511101) energized so that said magnetic fluid is solidified applying braking torque on said rotatable member; said winding being adapted when energized to produce flux in said casing. in a direction to I oppose saidpermanent flux so that no permanent f'magnet flux traverses said last mentioned air 'gapswhereby the nu produced bysaid winding diverts a portion of said magnetic fluid mixture irom said last mentioned air gaps to said ci'r- 'cumferential groove in said magnetic casing member releasing said braking torque.

7. A- clutch having a driving and a driven shaft, a rotatable member on one of said shafts comprising a permanent magnet polarized axial- 1y to form polar areas at its ends and a pair of annular fluxv conducting pole piece members respectively abutting the ends of said permanent magnet, the outer extremities of said pole piece members being space-dapart with adjacent faces ,standards, Washington, D. C. (Copy receive adjacent the outer circinnferential edges oi said pole piece members defining an air gap, and

an annular non-magneticspacer positioned in said air gap having a. circumferential groove formed in the outer surface thereof, andanother rotatable member on the other of said shafts surrounding said first rotatable member and comprising an annular exciting winding, a magnetic casing member surrounding said winding and having a circumferential groove formed in its inner circumferential surface, theinner circumferential surface portions of saidcasing on either side of saidcircu-mferential groove respectively forming air gaps with the outer circumferential edges of said polepiece members, said last mentioned air gaps having. magnetic fluid mixture arranged therein, said permanent magnet producing flux traversing said last mentioned air gaps and easing when said winding-is not energized sdthat said magnetic fluid. is s olidified forming. a driving connection between said rotatable members, .said Winding being adapted when energized to produce Number I fN'am e i f ...Dflt 1,303,48d Langdon-Davies May 13,. 1919 2,130,870v 'Boehne' Sept. 20, 1938 2,188,803 Boehne Jan. 30,1910

. 2,275,839 Boehne Mar, 10,1942 2,544,360 Schmidt Mar. 6, 1551 OTHER REFERENCES Technical Report 1213, National Bureauof (1 i Division 68, 11.8. P. 0., on March 30, liifiil 

